Demountable cable hydrophone



Filed Sept. 7, 1955 INVENTOR Maw? T. HARP/s BY I Z 5 I ATTORNEYS 2,864,07 3 DEMOUNTABLE CABLE HYDROPHONE Wilbun T. Harris, Southbury, Comm, assignor to The Harris Transducer Corporation, Woodbury, Conn., a corporation of onnecticut Application September 7, 1955, Serial No. 532,872 13 Claims. (Cl. 340-17) My invention relates to electroacoustic transducers, and, in particular, to constructions lending themselves to fabrication in an array. This invention incorporates improvements over those disclosed in my Patent 2,708,742 and in my copending application, Serial No. 502,434, filed April 19, 1955.

In the constructions of said patent and of said pending application, extreme ruggedness is achieved by solidly bonding longitudinally spaced hydrophone elements around the sheath of a multi-conductor cable including a tension core. In use, the core sustains virtually all the stress, and the likelihood of damage is substantially reduced. However, since the hydrophone is bonded to the cable, any malfunctioning of an individual hydrophone element represents a substantial loss, and maintenance becomes a severe problem.

It is, accordingly, an object of the invention to provide an improved transducer construction of the character indicated.

It is another object to provide an improved transducer construction lending itself to ready removable replacement on a hydrophone cable.

It is a general object to achieve all the objects of an integral hydrophone-cable construction, as described in said patent and in said patent application, while at the same time permitting ready removability of the individual hydrophone and/ or float elements to permit servicing.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specification, in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, preferred forms of the invention:

Fig. l is a simplified side view illustrating a surface vessel towing a paid-out length of hydrophonic cable incorporating features of the invention;

Fig. 2 is an enlarged fragmentary view, in partial longitudinal section, illustrating the hydrophonic cable of my invention;

Fig. 3 is a fragmentary view similar to Fig. 2, but illustrating a modification; and

Figs. 4 and 5 are simplified diagrams illustrating electrical connections for the cables of Figs. 2 and 3, respectively.

Briefly stated, my invention contemplates an improved transducer and float construction for removable application to an elongated continuous multi-conductor cable having a tension core and forming, when assembled to the cable, an elongated array, as for geophysical-prospecting applications. The hydrophone elements may be hollow cylindrical radially strictive members formed integrally into tubular assemblies, complete with reinforcement members and internal pressure-release means. In order to permit removable securing of the transducer assembly to the cable, the longitudinal ends thereof are provided with radial clamps; the float constructions may be essentially the same, involving radial clamps at the longitudinal ends. In the specific preferred forms to 2,864,073 Fatented Dec. 9, 1958 be described, the hydrophone assembly is contained within an elongated annular cup, having a continuous bore for reception of the cable and containing, within the annular space defined by inner and outer walls of the cup, all the necessary transducer elements, reinforcement members and pressure-release means. The parts within the annular space of the cup may be solidly potted in a hard sound-transmitting plastic and may exhibit the same rugged properties as those described in said patent and in said patent application.

Referring to the drawings, I indicate generally in Fig. 1 that my array may comprise a plurality of transducer elements 10 spaced longitudinally along a single cable 11 and suitably supported for the intended purpose. In the case shown in Fig. l, the cable is to be employed for underwater oil prospecting, and I show the cable 11 being payed out from a drum 12 supported at the stern of a towing vessel 13. The various hydrophones on the cable 11 may themselves be sufliciently neutrally buoyant, but, if desired, additional buoyancy may be provided by floats 14 spaced from the hydrophones 11. The float and hydrophone constructions are shown in greater detail in Fig. 2.

As will be seen from Fig. 2, the cable may be of the multi-conductor variety (as indicated schematically by spaced longitudinally extending lines 15) filling the annular space around a tension core 16, which may be a stranded-steel cable. For ready identification, the conductors 15 may be color-coded and they may be immersed in a layer or volume of insulating material 17; alternatively, the conductors 15 may be twisted as individual pairs, separately insulated, and merely packed around a plastic or rubber-coated stress core 16, the immersion in insulating material 17 being unnecessary in certain applications. A sheath or jacket 18 completes the construction of the cable 11 itself.

The assembly of the cable 11 may in all respects be conventional, except that I prefer, at each location where a hydrophone 10 is to be attached, that a different pair of conductors 15 (as, for example, the conductors 15 of Fig. 4) be brought into a slightly enlarged loop for electrical connection to each particular hydrophone. This loop may be gathered and knotted externally of the filling 17 before application of the sheath or cover 18, so that when the cover 18 is applied, a small bump in the outer contour will show where incision must be made to gain access to the desired pair of conductors 15. The cover 18 may be of tough plastic, such as vinyl, but I prefer to use rubber or a rubber-like material, such as neoprene.

In accordance with the invention, I provide hydrophone assemblies 10 and float assemblies 14, which are removably securable to the cable 11 so as to facilitate replacement of individual units for maintenance purposes. In the form shown, the individual transducer assemblies 10 each contain a plurality of longitudinally spaced, radially strictive, generally cylindrical hydrophone elements 2021. These elements 2021 and other parts of the transducer assembly are solidly potted within an elongated annular space, defined between the inner wall 22 and the outer wall 23; walls 2223 may be integral parts of an elongated annular cup of soundtransmitting yieldable material, such as rubber or neoprene or vinyl. Said cup is closed by an end section 24 at one longitudinal end and by a subsequently applied plug 25 of similar material at the other end. The end section 24 and the plug 25 preferably taper from a maximum diameter represented by the outer wall or sheath 23, to a lesser diameter defined by an elongated sleeve 2425', as the case may be.

The bores of the plug 25 and of the inner wall 22 of the cup are preferably of the same diameter so as to define a smooth, continuous bore for reception of the cable 11. The fit of the cable to this bore should permit snug but relatively free sliding of the hydrophone assembly along the cable, but once the desired longitudinal location of the cable has been achieved, circumferential clamps 2627 on the sleeve portions 24'25' may be set to anchor the hydrophone in place. Since thehydrophone assembly is fully potted and is a self-contained and sealed operating unit, regardless of its assembly to the cable 11, the seal of cable sheath 18 to the bore of the hydrophone assembly is not critical, and circumferentially continuous end clamping at 2627 suflices.

The provision for reinforcement and pressure-release within the hydrophone assembly may be much the same as described in said patent and in said patent application. Thus, the annular space within the cup 222324 may contain an elongated tubular reinforcement member 28, as of steel or aluminum. The member 28 extends beyond the longitudinal limits of the transducer elements 2021 and supports rigid reinforcement rings or bulkheads 29--30, extending to the outer wall 23 of the tube and therefore radially outside the outer limits of the transducer element 2021. A layer 31 of pressure-release material, such as cork, may be wrapped around the reinforcement member 28 in the spaces between bulkheads 29-30, so as to provide pressure-release radially inside the strictive members 2021. The strictive members 2021 are shown as of piezoelectric ceramic, such as barium titanate, and include inner and outer foil electrodes with connections 33 in parallel for the respective elements 20-21 of each hydrophone assembly 10. The external leads 34 may be brought out through holes in one of the end bulkheads 29 and radially inwardly through the inner wall 22 of the cup (i. e. at the open end of said inner wall 22). A hard plastic potting 35 may be applied by vacuum techniques and preferably bonds all the described parts withinthe cup 222324 and solidly covers the ends of the external leads 34, so as not to expose these ends at the open end of the cup 222324. In this manner, placement of the plug need not be relied upon to preserve insulation or otherwise to protect the leads 34.

In elongated piezoelectric hydrophone cables of the character indicated, it is important to note that unless enough hydrophone elements are employed at each source location (e. g. for the two transducer elements 2021 of the single unit of Figs. 2 and 4) to make the source capacitance high compared to the stray capacitance between lead circuits in the cable, then capacitative cross-talk is likely; in such event, a small impedance transformer 36 may be carried by each transducer unit 10 and serve to couple the elements -2li to the lead pair 15 associated therewith. In Fig. 2, I show that the impedance transformer 36 may conveniently be potted within a suitable protective recess 37 at one end of the reinforcement cylinder 28.

It is desirable that the overall density of the hydrophone unit 10 shall be kept to a minimum, consistent with structural rigidity. To this end, the pressure-release means 31 may be of substantially greater volumetric proportions than those shown in the drawings, so as to render the hydrophone cable more neutrally buoyant; however, in the form shown, additional float members 14 are interlaced with hydrophones 10 along the cable. The construction of float 14 generally resembles that described in said patent, except that provision is made for removable replacement for maintenance purposes. Thus, the ends 4041 of the boot 42 may be elongated sleeves slidably receivable on the cable 11 and carrying circumferential clamping mechanisms 4344, resembling the clamps 2627 for the hydrophone assembly 10. The air volume 45 within the float 14 is maintained by a rigid tubular construction 464748, supported on the cable body, and sealed oil at 4t)41.

Fig. 3 illustrates another hydrophone construction resembling that of Fig. 2 in all respects except for the maintenance that is thereby permitted while in no way sacrificing the ruggedness which is characteristic of the arrays of my said patent and of my said pending application. In order to apply a hydrophone assembly 10 to the cable 11, it is merely necessary that the clamps 2627 be slacked oif so as to allow free slipping of the hydrophone assembly along the length of the cable. The particular conductor pair 15 to which the hydrophone assembly is to be connected should be stripped for connection to the leads 34. After connection, as by soldering, and after sealing the connections, the hydrophone assembly should be further slipped along the cable so' that all parts of leads 15'34 are fully accommodated and hidden between the clamps 26-27. The assembly is then tightly secured by setting the clamps 26-27. For maintenance purposes, the only break that is necessary is in the lead connections (15' to 34) but to break these connections in no way impairs the subsequent usefulness of the cable, as after a damaged hydrophone element has been replaced.

While I have described the invention in detail for the preferred forms shown, it will be understood that modifications may be made within the scope of the invention as defined in the claims which follow.

I claim:

l. A hydrophone construction, comprising an elongated annular cup of yieldable sound-transmitting material having inner and outer tubular walls and open at one longitudinal end and closed at the other and defining an annular space between said inner and outer walls, a. generally cylindrical radially strictive hydrophone member within said space, a potting of sound-transmitting material filling the remainder of said space and bonding said member to said inner and outer walls, said pot tin-g completely encasing said member and serving to close the open end of said cup, said cup having an elongated continuous 'bore coaxial with said space, an elongated tension cable passing through said bore, and means removably securing said cup to said cable.

2. A hydrophone construction, comprising an elongated annular cup of yieldable sound-transmitting material, said cup having inner and outer tubular walls, the inner of said walls defining a central continuously open bore for receiving a continuous tension cable therein, said cup being open at one longitudinal end and closed at the other and defining between said inner and outer cylin- 'drical walls an annular hydrophone-element space, a

cylindrical radially strictive hydrophone element in said space and in potted intimate sound-transmitting relation with said cup, and means integrally bonded to said cup at both inner and outer walls thereof and closing oil? the open end of said cup.

3. A- hydrophone construction, comprising an elongated annular cup of yieldable sound-transmitting material having an elongated continuous bore for reception of a continuous tension cable, a hollow generally cylin' drical radially strictive hydrophone element encased in and supported by said cup and coaxially surrounding.

said bore, a plug bonded to the open end of said cup and sealing said hydrophone element within said cup, and radial clamping means at said plug and at the closed end of said cup for clamping said hydrophone construction to a cable which passes through the bore of said cup.

4. A hydrophone construction, comprising a tubular cylindrical reinforcement member, a hollow generally cylindrical radially strictive hydrophone element generally coaxial with said tubular member and surrounding the same, a layer of pressure-release material radially between said element and said member, a potting of sound-transmitting material integrally bonding said hydrophone element to said reinforcement member and fully encasing said hydrophone element, and releasable radially acting clamps carried at the longitudinal ends of said bonded assembly for securing the same to a tension cable passing through said tubular member.

5. A hydrophone construction according to claim 4, and including an inner sheath of rubber-like material bonded to said tubular member and extending beyond the longitudinal ends thereof and supporting said clamps at said extended'ends.

6. A hydrophone construction, comprising a longitudinal tubular reinforcement member, a hollow generally cylindrical radially strictive hydrophone element spaced from and surrounding a portion of said reinforcement member, a pressure-release layer radially between said hydrophone element and said tubular member, circumferentially extending rigid reinforcement means extending radially outwardly of said tubular member at longitudinally spaced locations beyond the respective longitudinal ends of said hydrophone element, said rigid reinforcement means extending radially outwardly beyond the outer radial limits of said hydrophone element, a potting of sound-transmitting material bonding said hydrophone elements within the annular space defined between said rigid reinforcement means, and releasable cable clamps carried by said assembly at the longitudinal ends thereof for releasably securing said assembly to a tension cable passing through said tubular reinforcement member.

7. A hydrophone construction, comprising an elongated annular cup of yieldable sound-transmitting material, said cup having inner and outer tubular walls and being closed at one longitudinal end and open at the other and defining an annular space between said walls and said ends, a tubular reinforcement member lining the inner wall of said space, a cylindrical radially strictive hydrophone element surrounding said tubular reinforcement member and located in said space, a pressure-release layer radially between said hydrophone element and said tubular member, a potting of sound-transmitting material bonding said parts Within said space, and an annular plug bonded to the closed end of said cup and sealing the bonded parts within said cup, said plug and cup having aligned bores, whereby a clear continuous passage may be presented for reception of said hydrophone construction on a tension cable.

8. A construction according to claim 7, in which said pressure-release layer is a sheath of cork.

9. An electroacoustic array, comprising a continuous elongated multi-conductor cable with a tension core, a plurality of cylindrical hydrophones enveloping and coaxially supported by spaced continuous parts of said cable and electrically connected to different conductors in said cable, each said hydrophone including removably securable clamping means whereby said hydrophones may be removably secured to said cable, and a plurality of hollow cylindrical members enveloping and coaxially supported by other spaced continuous parts of said cable and radially spaced from said cable, and means removably sealing the ends of said cylindrical members to said cable whereby said array may be neutrally buoyant.

10. A hydrophone construction, comprising an elon gated annular cup of yieldable sound-transmitting material having a closed end and an open end and defining between radially inner and outer walls an annular hydrophone-receiving space, an elongated tubular reinforcement member within said space, a cylindrical piezoelectric hydrophone element surrounding said tubular member and potted to said cup within said space, and releasable securing means carried at the longitudinal ends of said cup for releasably securing the same to a tension cable passing through the bore of said cup.

11. A hydrophone construction, comprising an elon- "gated annular cup' of yi'eldable sound-transmitting material having a closed end and an open end and defining between radially inner and outer walls an annular hydrophone-receiving space, an elongated tubular reinforcement member within said space, a cylindrical magnetostrictive hydrophone element surrounding said tubular member and potted to said cup within said space, and releasable securing means carried at the longitudinal ends of said cup for releasably securing the same to a tension cable passing through the bore of said cup.

12. An electroacoustic array, comprising a continuous elongated multi-conductor cable with a tension core, a plurality of annular hydrophone assemblies having bores slidably accommodating said cable and being longitudinally spaced along said cable, said hydrophone assemblies being connected to said conductors intermediate the longitudinal ends of said assemblies, and circumferentially extending releasable clamps at both longitudinal ends of each hydrophone assembly and anchoring both ends to said cable.

13. A hydrophone construction, comprising an elongated annular cup of yieldable sound-transmitting material, said cup being closed at one longitudinal end and open at the other and defining an annular space between said ends, a tubular reinforcement member lining the inner wall of said space, a cylindrical radially strictive hydrophone element surrounding said tubular reinforcement member and located in said space, a pressure-release layer radially between said hydrophone element and said tubular member, a potting of sound-transmitting material bonding said parts within said space, and an annular plug bonded to the closed end of said cup and sealing the bonded parts within said cup, said plug and cup having aligned bores, whereby a clear continuous passage may be presented for reception of said hydrophone construction on a tension cable, said plug and the closed end of said cup extending longitudinally beyond the limits of said tubular member, and radial-compression clamping means carried by said plug and by said closed end, respectively, for clamping the longitudinal ends of said construction to a tension cable.

References Cited in the file of this patent UNITED STATES PATENTS 2,440,903 Massa May 4, 1948 2,708,742 Harris May 17, 1955 2,722,667 Huston Nov. 1, 1955 

